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UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 643 

Contribntion from the Bareaa of Entomolog/ 
L. O. HOWARD, Chief 



Washington, D. C. 



March 8, 1918 



THE MELON FLY 



By 

E. A. BACK, Entomologist 
and C. E. PEMBERTON, Assistant Entomologist 

Mediterranean and Other Fruit Fly Investigations 



CONTENTS 



Page 

What the Melon Fly is Lilce ..... 3 

OrifTin and Distribution 4 

Establishment and Spread in Hawaii . . 4 

Methods of Spread 7 

Economic Importance 7 

Nature of Injury Caused by the Melon Fly 8 

Food or Host Plants 16 



Page 

Interesting Facts Concerning the Adult Fly 22 

Why the Melon Fly is a Serious Pest . . 24 

Control Measures . . 2S 

Measures Taken to Keep Fruit Flies of 
Hawaii from Gaining a Foothold in Con* 

tinenUl United States 29 

Summary SO 




WASHINGTON 

GOVERNMENT PRINTING OFHCB 

1918 



THE MELON FLY is a truck-crop pest that in 
the course of international commerce has been 
spread from its native home in the Indo-Malayan 
region to the Hawaiian Islands, and has become so 
thoroughly established that it can not be eradicated. 
Owing to its destructive work, such fruits as musk- 
melons, watermelons, pumpkins, squashes, cucum- 
bers, vegetable marrows, and tomatoes can not be 
grown to-day in many parts of the Hawaiian Islands 
unless the plants are screened. Cantaloupes and 
watermelons, instead of being common and cheap 
delicacies, as in former years, are now a luxury 
even for the wealthy; and cantaloupes, formerly 
grown in quantities about Honolulu, are now im- 
ported from California. Owing to the danger of 
introducing the melon fly into countries where it 
does not now exist, quarantines prohibit the export 
of Hawaiian-grown eggplant, bell peppers, and 
tomatoes, thus shutting off an income formerly 
enjoyed by the small farmer. In short, it is not 
possible to exaggerate the seriousness of this insect 
under Hawaiian coastal conditions. 

The problem, however, is not entirely a local one 
to be fought out by the people of Hawaii. Should 
the melon fly once break through the Federal quar- 
antine barriers and become established on the main- 
land of the United States, it will exact a large 
annual toll of the truck crops of the South. It is 
important, therefore, that truck growers learn some- 
thing about this pest, so difficult of control, in order 
that they may become actively interested in keeping 
it out. 



D. of D, 
MAR 15 1918 






UNITED STATES DEPARTMENT OF AGRICULTURE 




1^ BULLETIN No. 643 



Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 




jdk^'^U 



Washington, D. C. 



March 8, 1918 



THE MELON FLY.^ 

By E. A. Back, Entomologist, a-nd C. E. Pembekton, Assistant Entomologist, 
Mediterranean and Other Fruit Fly Investigations. 



CONTENTS. 



What the melon fly isKke , 

Origin and distribution 

Establishment and spread in Hawaii 

Methods of spread 

Economic importance 

Nature of injury caused by the melon fly 
Food or host plants 



Interesting facts concerning the adult fly 22 

Why the melon fly is a serious pest 24 

Control measures 25 

Measiu-es taken to keep fruit flies of Hawaii 
from gaining a foothold in continental 



United States. 



IC) Summary. 



THE MELON FLY is a serious pest that never slioiild have 
gained access to the Hawaiian Islands. Its establishment in 
Hawaii came naturally enough, as in the case of many of our worst 
insect enemies, along with the development of unrestricted modern 
commerce, and owing to the lack, in earlier days, of a knowledge of 
pests in other lands likely to be introduced into ours, or of any 
quickened public opinion which, at last thoroughly alive to the 
great financial losses that may be averted, is to-day heartily sup- 
porting Federal quarantines directed against just such pests as 
the melon fly. 

The melon fly is now established thoroughly throughout the 
coastal regions of the Hawaiian Islands and never will be eradi- 
cated. It attacks many vegetables that otherwise could be grown 
readily by the poorer people, who are least able to purchase them. 
Melons, pumpkins, squashes, cucumbers, and tomatoes, and some 

1 Bactrocera cucuriitae Coq. ; order Diptcra, family Trypetidae. 

For a more extended account of the melon fly see Back, B. A., and Pemberton, C. E. 
The melon fly in Hawaii. U. S. Dept. Agr. Bui. 491. 64 p., 24 pi., 10 fig. 1917. This 
may be obtained from the Superintendent of Documents, Government Printing Office, 
Washington, D. C, for 25 cents. 

Note. — The manuscript of this paper was prepared for publication as a Farmers' Bul- 
letin, but owing to the fact that it deals with an insect which has not yet been introduced 
into the continental United States it was considered more appropriate to issue it in the 
series of Department Bulletins. 

18314° — 18 — Bull. 643 1 



BULLETIN 643, U. S. DEPARTMENT OF AGEICULTUEE. 



other A'egetables to-day can not be grown in many parts of the islands 
except Avith great effort ; they must be imported from across the sea, 
as a result of melon-fly attack. 

The melon fly is capable of living and causing damage through- 
out the warmer portions of the mainland United States. As it is 




Fig. 1. — Tip of watermelon vine, sliovving adult melon fly laying eggs in ovary of a flower 
still in bud, an unaffected male bloom, and withered and drooping growing tip of vine. 
A female melon fly has deposited eggs in the vine at base of leafstalk, and the young 
larvae hatching have nearly severed the vine at this point. (Authors' illustration.) 

being intercepted rather frequently by official inspectors at Cali- 
fornia ports on ships from Hawaii, the importance of cooperation by 
all in making the quarantine of the Federal Horticultural Board a 
success in keeping out this very serious pest will be readily appre- 
ciated. 



THE MELON FLY. 3 

WHAT THE MELON FLY IS LIKE. 

The melon fly, like other so-called " fruit flies," is similar to the 
ordinary house fly in some respects ; the adult lays small white eggs 
from which hatch larvae, or maggots, which when full grown trans- 
form into pupa3. Later the adult emerges from the pupa, as the 
butterfly does from the chryalis, and the cycle of life — adult, egg, 
larva, pupa — is repeated with each successive generation. Fig- 
ure 1 shows an adult melon fly about to lay eggs in the bud of a 
watermelon. Note the relative size of the fly and the bud. The 
adult female, greatly enlarged, is shown in figure 2. ^Vlien it is 
remembered that the adult is from one-fourth to one-third of an 
inch long, that its body is of a A^ellowish to a yellowish-brown color, 




Fig. 2. — Adult female of the melon fly. Greatly enlarged. (Authors' illustration.) 

and the markings between the wings, which appear white in the 
figure, are bright canary yellow in the living insect, and that the 
wings are banded Avith dark brown, it will not be difficult to recog- 
nize this pest. 

The female fly drills small, pinhole-like openings in the skin of 
vegetables with the sharp tip of her body, called the ovipositor. 
Through these punctures she lays her white eggs, Avhich are about one 
twenty-fifth of an inch long. If a small squash flower be cut open 
after the female fly has laid her eggs, a small cavity containing the 
eggs, such as is illustrated by figure 3, is shown. The larvse, or mag- 
gots, that hatch from the eggs feed in various parts of the host plant. 
They have two black hooklike processes in the head that serve as 
jaws in aiding them to break up their food and to force their way 



BULLETIN 643^ U. S, DEPARTMENT OF AGRICULTUKE. 



through the phxnt tissues. But as the hirvse, even when full grown, 
are only about two-fifths of an inch long, a detailed description of 
them is of little value. It is enough to know that they differ very 
little from the ordinary white maggots, of equal size, with which 
the reader is doubtless familiar. The larvae when full grown leave 
the host to transform to the pupa stage just beneath the surface of 
the soil, or beneath any protecting object. They even may transform 
to the pupa within the host fruit, but this is a rare occurrence. Figure 
4 shows larvae and pupae about twice natural size. 
In figure 6 are shown well-grown larvae feeding in 
the root of a young watermelon plant. Figure 5 
represents an enlarged larva. 

As the melon fly usually first forces itself upon 
the attention of the market gardener by the dam- 
age it does, it is more important to be able to recog- 
nize it by its work than by a mere description of 
the different stages. The reader, therefore, is 
directed particularly to the illustrations, for, be- 
sides showing types of injury, they make clear 
that it is in the lars^a stage that the melon fly 
causes its greatest damage. 

ORIGIN AND DISTRIBUTION. 

The original home of the melon fly is the Indo- 
Malayan region. At present it is known to occur 
in various parts of India, in Ceylon, Java, Macao, 
Timor, northern Australia, about Singapore, in 
southern China at Canton and Hongkong, in the 
Philippine Islands, in Formosa, and in the Ha- 
waiian Islands. There is some doubt at present 
about its occurrence at Nagasaki, Japan. 

It is believed that the melon fly was introduced 
into the Hawaiian Islands at Honolulu from 
It probably arrived in the larva stage in vege- 
tables brought along as food from Japan by Japanese coolies emi- 
grating as steerage passengers to work on the sugar plantations in 
Hawaii. 

ESTABLISHMENT AND SPREAD IN HAWAII. 




Fig. 3. — The melon 
fly : a. Eggs de- 
posited in cavity 
In young pumpkin 
flower ; h, single 
egg, much en- 
larged. ( Authors' 
illustration.) 

Japan or China. 



The melon fly was first observed in Hawaii, so far as records show, 
by Mr. Byron O. Clark, who, during October to December, 1897, 
found it almost impossible to grow cucumbers, squashes, melons, and 
similar vegetables in the Kalihi district of Honolulu and about Pearl 
City. During August, 1898, the pest already was established at Lau- 



THE MELON FLY. 5 

pahoehoe, Island of Hawaii. Indications are that the melon fly was 
introduced as early as 1895. 

That the melon fly is an introduced pest is proved by the inter- 
esting fact that the gourd calabashes used by the Hawaiian natives 
during the past century, many of which are preserved in various 




Fig. 4. — Melon fly: a. Well-grown larva;; b, puparia. Twice natural size. (Original.) 







Fig. 5. — The melon fly : Third-instar larva, a. Lateral view of entire body ; b, dorsal view 
of anterior end ; c, d, lateral and ventral views of same. Much enlarged. (Authors' 
illustration.) 

museums and private collections, are free from evidences of melon- 
fly attack. Modern utensils largely have superseded calabashes dur- 
ing these later days, but the few that are gi'own show the surface 
defects due to the attack of the melon fl}^ 

Although no satisfactory record has been made of the spread of 
the melon fly to the various islands of Hawaii, it is now a well- 



BULLETIN 643, U, S. DEPARTMENT OF AGEICULTUEE. 




Fig. G. — 1, Watermelon seedling destroyed by larvffi of melon fly foodins in taproot, 
crown, and leaf petioles; 2, work of larvae in root, enlarged. (Authors' illus- 
tration.) 



THE MELON FLY. 7 

established and serious pest throughout all the coastal regions. It 
has been known even to attack cucumbers and squash at altitudes 
ranging up to 4,000 or 4,500 feet. 

METHODS OF SPREAD. 

The melon fly probably is carried more often from one locality 
or country to another in the larva stage than in any other form. 
Quarantine officials at San Francisco have found living larvsc in 
host fruits arriving at San Francisco on ships from Honolulu, and 
records prove that the melon fly in the larva stage is able to bridge 
the six or seven days required by the slower vessels to cover the 2,000 
miles between the Hawaiian Islands and California, since infested 
fruits have been intercepted and condemned at least once a year 
since 1912. Host fruits taken on board ships as ship's stores are 
capable of carrying the melon fly as larvae, or later as pupae, in the 
fruit containers, for voyages occupying a longer time than is re- 
quired to cross the Pacific Ocean, and thus may become a factor in 
spreading the pest through vessels plying between almost all coun- 
tries where climatic conditions are favorable for the establishment 
of the fly. 

The spread from one country to another at a considerable distance 
probably starts with the fly in the larva stage, but the spread from 
town to town, or over short distances, as between islands of the 
Hawaiian group, may occur in the adult or pupa stage. A female fly 
has been observed to alight on an automobile top and be carried 16 
miles from the country into the city of Honolulu. On another occa- 
sion an adult was seen flying about an interisland boat en route from 
Honolulu to Hilo, on the island of Hawaii. This fly was not observed 
after the boat weighed anchor at the port of Lahaina, on the island 
of Maui, or 72 miles from Honolulu. These two instances will ex- 
plain the spread of the pest, in the adult stage, about the islands of 
Hawaii, even if it could not be transported in the larva stage. 

When larvae form their puparia on bare surfaces, and particularly 
on a cloth surface, the puparia may adhere sufficiently well to make 
it possible for them to be transported considerable distances under 
favorable circumstances. Although no definite instances are known 
where the melon fly has been spread thus, distribution in this fashion 
is quite feasible and to be expected. 

ECONOMIC IMPORTANCE. 

The melon fly is the most important pest of varieties of melons, 
squashes, and curcurbits in general grown in the Hawaiian Islands, 
and probably elsewhere. Its persistent attack has caused many per- 
sons to abandon the growing of the more susceptible host fruits. 



8 



BULLETIN 643, U. S. DEPARTMENT OF AGRICULTURE. 



Other fruits can be grown for the most part only under cover and at 
increased cost. The unrestricted cultivation of fruits and vegetables 
in Hawaii has been ruined by the melon Hy and the Mediterranean 
fruit fly. Though the latter is probably the more to be feared, many 
persons regard the melon fly as of greater im- 
portance from an Hawaiian standpoint, for it 
attacks with the gi'eatest persistency such crops 
as squashes, pumpkins, vegetable marrows, to- 
matoes, and beans, all of which could furnish 
under the ideal Hawaiian climatic conditions 
an abundance of food for the poorer people. 
Such vegetables as muslanelons, watermelons, 
pumpkins, squashes, and tomatoes can not be 
grown to-day in many parts of the islands 
unless the plants are screened carefully. 

Cantaloupes and watermelons, instead of be- 
ing common and cheap delicacies, as in former 
years, are now a luxury for even the wealthy. 
Cantaloupes, once grown in large quantities 
about Honolulu, now are imported from Cali- 
fornia. It is no longer possible to grow pump- 
kins as stock food on idle land. Quarantines 
prohibit the export of early shipments of egg- 
plant, bell peppers, and tomatoes, thus shut- 
ting off an income formerly enjoyed by the 
small farmer. The loss to market gardeners in 
Hawaii as a result of melon-fly attack has been 
placed conservatively at three-fourths of a mil- 
lion dollars annually. It is not possible to 
exaggerate the importance of the melon fly 
as a serious pest under Hawaiian coastal con- 
ditions. 

NATURE OF INJURY CAUSED BY THE 
MELON FLY. 



Fig. 7. — Older squasb 
vine with abnormal 
growths due to work 
of melon-fly larvje. 
(Authors' illustra- 
tion.) 



The melon fly does not confine its attack to 
the fruits of its host or food plants. It may 
attack the young seedling, the flower, the root, 
the stem, or the fruit. 



INJURY TO SEEDLING PLANTS- 



The melon fly attacks with severity the young succulent seedling 
plants of watermelon and cantaloupe. The female fly lays her eggs in 



THE MELON FLY. 9 

the crown of the plant, and the larvae, on hatching, feed there first. 
They later burrow down into the taproot and upward into the 
petioles of the leaves, and even into any young runners that are form- 
ing. The capacity of the melon fly for injuring a watermelon seedling 
is shown in figure 6 (p. 6). The enlarged figure of the root shows 
four full-grown larvae eating their way into the root. In the figure 
of the seedling the larvae have almost severed the leaf to the left, 
and have tunneled completely through one of the petioles and so 
destroyed it that the weight of the leaf has caused its stem to break 
over. Injury to a seedling runner is shown in figure 8. In cer- 
tain places in Hawaii where the melon fly is very abundant, entire 




Fig. 8. — Seedling watermelon showing runner killed back by burrowing melon-fly larvse. 

(Authors' illustration.) 

fields of watermelons may be killed before the plants can develop 
runners. Squash, pumpkin, cucumber, tomato, and bean seedlings 
almost never are attacked. Larvae never are found in the roots of 
older plants. 

INJURY TO THE STEM. 

As the plant becomes older, it is still subject to attack. The female 
fly lays her eggs in the rapidly growing pumpkin and squash vines, 
but the larvae after hatching do very little damage, although they are 
able to mature. They often cause abnormal swellings or cancerlike 
spots where a colony of them are feeding, as illustrated by figure 7 ; 
but if the injury threatens the stem, the plant throws out roots on 
either side of the part affected to offset the damage. Such attacks 
upon the stem are not of importance, except in the case of watermelon 
and cantaloupe. 

18314°— 18— Bull. 643 2 



10 BULLETIN 643, U. S. DEPARTMENT OF AGEICULTUEE. 

But in the two plants last mentioned the injury resulting from 
attack upon the stems may be very serious, and in many cases cause 
a complete failure of the crop. Figure 9 shows a portion of a canta- 




PiG y._Cantaloupe vine attacked by melon fly in eight places, including stalk, leaf 
petioles, and young fruit. (Authors' illustration.) 

loupe vine that has been attacked in eight places. So persistent is 
attack upon cantaloupe in Hawaii that the vine can not be grown 
satisfactorily except in isolated spots or under cover. 



THE MELON FLY. H 

Figures 1 and 10 show a common condition found in watermelon 
fields. The female fly usually chooses the growing tip of the runners 
in which to lay her eggs. In making a place in the vine for her eggs 
she practically severs the tip of the vine so that it may fail to grow 




Fig. lu. — Succulent watermelon vine sectioned to expose five well-grown larvae of tlie 
melon fly which have eaten out the interior, causing the vine to wither and die back 
to the point of original infestation. (Authors' illustration.) 

beyond the point of injury. The growing end of the vine, however, 
usually is ruined, for, if the egg-laying process does not cause serious 
damage, the larvse hatching, numbering from 2 to 10, begin to feed 
and bring about a hasty destruction. Figure 1 shows the drooping, 



12 



BULLETIN 643, U. S. DEPAETMENT OF AGRICULTURE. 



withered, growing tip. In this case the eggs were laid just beyond 
the leaf and flower stalks. 

When the eggs are laid in the older though still very young and 
succulent watermelon vine, the larvae, on hatching, tunnel their way 




Fig. 11. — Melon-fly eggs in blooms of pumpkin. Two buds of the male bloom sectioned 
to show the eggs doposited through the corolla. (Authors' illustration.) 

through the vine, eating out the center and causing it to wilt and die. 
Figure 10 shows a vine sectioned to expose the five well-grown larvae 
Avhich have killed it beyond the base of the leaf in the upper left- 
hand corner of the illustration. The serious setback to vine develop- 



THE MELON PLY. 



13 



ment that this type of injury causes is readily apparent. Such prun- 
ing back of the vines, repeated over and again, may prevent the 
formation of sufficient growth 
for the development of fruits. 

INJURY TO THE BLOOM. 

Although injury to the seedling 
plant and to the growing stem is 
greatest in watermelon and can- 
taloupe and is of little importance 
among squashes, encumbers, and 
pumpkins, the injury to the 
bloom is very serious among all 
these crops except that of the cu- 
cumber. Among pumpkins and 
squashes both the male and fe- 
male blooms are affected; but 
among the watermelons, canta- 
loupes, chayotes, and Chinese 
marrows the male or staminate 
bloom escapes attack. It is not 
uncommon to examine luxuri- 
antly growing fields of squashes 
and pumpkins during the warm 
months and not find a single un- 
affected bloom. Uninformed 
growers often question why their 
vines set no fruits. The condi- 
tion of the blooms illustrated in 
figures 11 to 14 is the answer. 

The unfertilized ovaries of all 
cucurbit blooms are especially 
attractive to female melon flies. 
The flies lay eggs in the undevel- 
oped and unfertilized ovaries of 
the bloom before the blossom un- 
folds, and the larvae, on hatch- 
ing, often so ruin the ovaries, 
as indicated by their burrows 
shown in figure 12, that the 
flower never unfolds. In those 
varieties having long, narrow 
fruits the ovaries arje man}^ times 
so eaten out and decayed that the weight of the upper part of the bud 
causes the ovary to break (see fig. 13) . So complete is the destruction 




Fig. 12. — Work of melon-fly larvae in bring 
Ing about destruction of ovaries of 
pumpkin bloom even before the corolla 
has entirely withered. 



14 



BULLETIN 643, U. S. DEPARTMENT OF AGRICULTURE. 



of the ovaries of watermelon bloom that in dry weather the remains 
of the bloom wither and become minnmified, as shown in figure 15. 

An examination of the bnds of the male bloom in any field through- 
out the coastal regions of the Island of Oahu, particularly during 
the months from March to November, will reveal the severity of 
attack centered on this portion of the plant. 
Wherever the buds have been attacked, a whit- 
ish gumlike excretion exudes which hardens 
about the point of attack. On cutting the buds 
lengthwise, batches of eggs can be seen among 
the folds of the corolla, or in the stamens and 
receptacle, as shown in figure 11 (p. 12). As 
the eggs are pure white and are in clusters 
of 2 to 10 or more, they are seen easily with- 
out the aid of a lens. If the eggs have been 
laid from 2 to 6 days, the inside of the bud 
may have been already eaten out by the rap- 
idly developing larvsB. Buds attacked before 
they are half grown usually are destroyed com- 
pletely before the blossom unfolds. Figure 11 
shows three stages in the destruction of the 
staminate bloom. The bud « is a mass of 
decay within ; the stamens have been devoured 
and the larvae already have begam to burroAV 
about the base; h shows a bud that has been 
severed by the feeding of the larvae and nas 
fallen over under its own weight; and c is the 
upright stem of the bud, after the essential 
parts of the bloom have been ruined and have 
fallen to the ground. Although attack may 
occur so late in the development of the male 
bloom that the corolla can unfold, it is more 
often than not that eggs, or even young larva?, 
can be seen on the inside of the corolla when 
the flower is in full bloom. The melon fly never 
attacks the bloom after the corolla has unfolded. 




Fig. 13. — Pistillate 
bloom of squash in 
which larviE of the 
melon fly have so de- 
voured the unferti- 
lized ovary that the 
bloom is destroyed be- 
fore the flower can 
unfold. (Authors' 
illustration.) 



INJURY TO NEWLY SET FRUITS. 



The greatest destruction among fruits usu- 
ally occurs when they are very young, either 
before they are fertilized or just after they have set. At this 
stage of development the young fruits are expanding very rap- 
idly. Figure 16 shows the damage done to thrjee young pumpkin 
fruits. About the damaged areas calluses are formed by the fruit 
in an attempt to repair the damage, but this attempt seldom 



THE MELON PLY. 



15 



prevents secondary decays from starting, and these bring about the 
destruction of such portions as escape the hirvse. The sectioned 
pumpkin in figure 17 shows how a colony of larvae may eat into a 
young fruit, become full grown, and leave it without causing a com- 
plete destruction. It also shows how smaller, weaker colonies may 
develop in the outer portion of the pulp. 



INJURY TO OTHER FRUITS. 



Complete destruction of fruits by larvae of the melon fly rarely 
occurs after they have become 4 to 5 inches in diameter, for then 




Fig. 14. — Buds of male flowers of pumpkin damaged by larvae of melon fly, a, h, and c 
representing various stages in tlie destruction of tlie bloom. (Authors' illustration.) 

the portion of the fruit containing the seeds, or the part preferred 
by the larvse, is w^ell protected by the outer meaty pulp and by the 
rind. Such colonies of larvae as are then able to become established 
in pumpkins and squashes usually develop in the outer portions of 
the fruit and do not penetrate to the center. In cantaloupes, water- 
melons, cucumbers, and marrows, however, the larvae more easily may 
work their way down to the softer, central portions and there com- 
plete their development, while the outer portion of the fruit remains 
quite firm. Figure 19 (p. 20) shows the cross section of a water- 
melon that had the general external appearance of being sound. 



16 



BULLETIN 643, U. S. DEPAETMENT OP AGRICULTURE. 



Yet, when cut open, it Avas found that its center had been eaten away 
entirely and the well-grown larvae had made tunnels, shown some- 
what reduced, throughout the rind. 

Numerous similar examples of destruction might be described. 
But it is important to remember the fact that melon-fly attack upon 
the older fruits is far more likely, except in the case of the canta- 
loupe, cucumber, and tomato, to result in larval development in open 

surface wounds and 
in deformities. 

One of the squashes 
of figure 21, the cu- 
cumbers of figure 18, 
and the watermelon 
of figure 20 illustrate 
types of deformities 
very common in Ha- 
waii. Wherever the 
fruits have been only 
slightly damaged by 
melon-fly attack, de- 
formities ; result. It 
is seldom that a per- 
fectly formed cucur- 
bit is seen in the 
markets of Honolulu 
unless the fruit was 
grown under protec- 
tive coverings. Al- 
though deformities 
do not completely 
ruin the fruit, they 
restrict development 
and prevent the fruit 
from reaching its 
normal size, as illustrated by the unaffected squash and the badly 
deformed squash of figure 21 (p. 22). Cucumbers and watermelons 
so badly deformed as those shown in figures 18 and 20 are not salable, 
even though they contain no larvae. The purchaser of finiit has 
learned from experience that deformed cucumbers must be viewed 
with suspicion, for, although they may be fit for the table, they may 
contain maggots. 

FOOD OR HOST PLANTS. 

The food or host plants of the melon fly may be divided into those 
preferred and those occasionally infested and may be listed as 
follows : 




Fig. 15. — Soction of watermelon vine, showing two fruits 
so devoured by larvaa of the melon fly that they have 
become mummified during dry weather following attack. 
Note that the remains of the blossom still persist. 
(Authors' illustration.) 



THE MELON FLY, 



17 



1. Cantaloupe. 

2. Watermelon. 

3. Pumpkin. 

4. Squash. 

5. Gourds. 



1. Eggplant. 

2. Water lemon 

flora sp.). 



1. Sycos sp.- 



]. Kohlrabi. 



(Passi- 



CULTIVATED. 

Preferred. 

6. Chinese cucumber 

{Momordica sp.). 

7. Chinese melon. 
S. Chayote. 

9. Cucumber. 

Occasionally infested. 

3. Orange. 

4. Fig. 

5. Papaya. 



10. Tomato. 

11. String beans. 

12. Cowpeas. 



6. Peach. 

7. IMango. 

8. Citrullus (.Tava). 



WILD. 

2. Momordica sp. 
Erroneously recorded host fruits. 

2. Cabbage. 3. Peppers. 



CUCURBITACEOUS PLANTS. 

All the cuciirbitaceous 
plants are subject to severe 
infestation, particularly 
of the young fruits. 
Cantaloupes are the most 
susceptible, since the Amines 
as well as the fruit are 
attacked badly at all 
stages of growth, and the 
fruits do not appear to 
develop the resistance to 
attack found among the 
older watermelons, pump- 
kins, and squashes. Ordi- 
narily the cucumber is 
resistant to attack when 
very young, although it is 
rare that cucumbers of- 
fered for sale in Honolulu 
do not shoAV some evidence 
of attack, even w hen 
very carefully collected. 
Cantaloupes and cucum- 
bers may be used success- 
fully by the female fly for 
egg laying up to the time 




Fig. 16. — Various deformities of very young pump- 
kins caused by infestations started before or just 
after fertilization of the ovary. These fruits per- 
sist for a time, owing to calluses developing about 
points of attack, but they never reach a much 
larger size and are ultimately destroyed by fungi 
and secondary attack. (Authors' illustration.) 



18 



BULLETIN G4;j, U. S. DEPARTMENT OF AGRICULTUEE. 



of 
un- 
not 

to 



they are ready for market. Although cantaloupe growing has been 
abandoned practically in Hawaii since the advent of the melon fly, 
cucumbers are grown without protection of any sort. Practically all 
fruits reaching a size fit for salad use show evidences of attack at one 

or more spots, but 
the i^ercentage 
fruits rendered 
marketable is 
large enough 
force the oriental 
growers to cover 
the young fruits, 
although it would 
appear disastrous^ 
large to American 
market gardeners, 
who place a high 
value on their time. 
During midwinter 
150 out of 153 cu- 
cumbers, ready for 
the market at Moi- 
liili, were found in- 
fested varioush\ 

All cucurbits grow 
with such rapidity 
in Hawaii that the 
oriental is willing to 
permit the pest to 
destroy fully 50 per 
cent of the fruits 
rather than go to the 
expense of covering 
each fruit as soon as 
or before it sets. To 
prevent wholesale in- 
jury, all cucurbits 
except cucumbers 
must be covered be- 
fore or just after 
blooming. 

Aside from the 
fact that the seedlings and vines of all cucurbits except canta- 
loupe and watermelon are attacked but slightly, there is little differ- 
ence in the susceptibility to attack of the young fruits under 




Fig. 17. — Cross section of young pumpkin, showing worlt 
of larvae of melon fly. Each affected area represents 
the location of a colony of larvae. (Authors' illus- 
tration.) 



THE MELON FLY. 



19 



Hawaiian conditions. Inasmuch as the fly has been permitted to 
increase unchecked since its introduction, it has become so abundant 
that slight differences in inherent resistance to attack are not evident 




Fig. 18.— Damage to cucumbers by larva? of melon fly. (Authors' Illustration.) 



among host fruits growing in the field. The infestation is ex- 
cessive in all unprotected fruits. If by chance pumpkins, squashes, 
and watermelons escape infestation until they are from 4 to 6 inches 



20 BULLETIN 643^ U. S. DEPARTMENT OF AGRICULTURE. 

in diameter they may reach maturity, although before they reach 
maturity pumpkins and squashes may support numerous colonies of 
larvae in open surface wounds and become badly deformed. Out of 
254 nearly full-grown pumpkins growing at Kahuku during the 
winter months, 250 were found variously deformed. As many as G50 
adults have been reared from a pumpkin not more than 4 inches 
long; the staminate bloom while still a bud may support as many 
as 37 well-grown larvae. 

TOMATOES. 

Tomatoes are very susceptible to attack. All tomatoes offered for 
sale in Honolulu are likely to be infested, as shown by the reports of 




Fig. 19. — Cross section of young watermelon, showing destruction of interior by larvae of 
melon fly. Reduced one-fourth. (Authors' illustration.) 

the market fruit-fly inspector covering several months. Fifteen ripe 
or partly ripe fruits examined at Hauula on March 21, 1915, con- 
tained eggs or larvae. Such severe infestation is so general during 
the warmer months that data are superfluous. Under climatic condi- 
tions less favorable for the increase of the melon fly the tomato 
probably would be found to be less susceptible to attack than cucur- 
bitaceous crops. The fruits of the small wild tomatoes and the spiny 
yellow-fruited Solanum, common in Hawaii, all are found growing 
about fields of cucurbit aceous croj)s, but never yet have been found 
infested. During January and February fields of tomatoes may pro- 
duce a large percentage of sound fruits, owing to the effect of the 



THE MELON FLY, 



21 



cooler weather upon the activities of the fly. Only the fruits of the 
tomato are subject to attack. 

STRING BEANS. 

The ordinary varieties of string beans grown on the mainland as 
a rule are not infested by the melon fly. Of the variety commonly 
known as the Yellow Wax bean, 375 pods sufficiently ripe to have 
turned color were ex- 
amined at Haleiwa and 
were found free from 
attack, although grow- 
ing close to a field of 
badly infested pump- 
kins, in March. Exami- 
nations of string beans 
in other localities, par- 
ticularly about Hono- 
lulu, indicate that 
seldom are any of the 
varieties infested ex- 
cept the more fleshy, 
long-podded Chinese 
variety. This varietj'^ 
may be attacked very 
badly when grown 
near other favored 
host fruits or on land 
recently cleared of 
such crops, as illus- 
trated by figure 22. As 
many as 36 well-grown 
larvae have been found 
within a single pod. 

Although the Chi- 
nese variety is the only 
one at times generally 
and badly affected, 
beans of all varieties 
except the Lima bean should be included in quarantine lists. The 
Lima bean never has been found infested. Only the pods of beans 
usually are infested. The larvae prefer to feed upon the fleshy por- 
tions of the pod, but sometimes attack the seeds. In badly infested 
pods, attacked before the seeds are well grown, the larvae may eat out 
the seeds and leave nothing but the outer portion untouched. This 
also is true of cowpeas. 




Fig. 20. — Deformed watermelon resulting from late in- 
festation by larvse of melon fly. (Authors' illustra- 
tion.) 



22 BULLETIN 643^ U. S. DEPARTMENT OF AGRICULTURE. 

COWPEAS, 

Although cowpeas are not grown to any great extent in Hawaii, 
they are subject to melon-fly attack. Only the pods are affected. As 
many as 37 larvae have been taken from a single pod. When infesta- 
tion occurs early the young seeds may be devoured, but attack is cen- 
tered more often upon the pod itself. Some varieties of cowpeas 
appear to be less liable than others to attack by the melon fly. 

FRUITS AND VEGETABLES THAT ARE SELDOM OR NEVER ATTACKED, 

Several observers have stated that the melon fly attacks eggplant, 
bell peppers, cabbage, and kohlrabi. During a period of three years 

the representatives of 
the department have 
not found any of 
these vegetables af- 
fected. The Mediter- 
ranean fruit fly has 
been found attacking 
eggplant and bell 
peppers, but only in 
small numbers. Even 
in the laboratory egg- 
plant was found im- 
mune to melon - fly 
attack if the fruits 
were spund. Adult 
melon flies, however, 
wei'e reared from 
fruits first weakened 
by decays. 

Adults have been 
reared from orange, 
mango, fig, papaya, 
peach, apple, and 
water lemon. These 
fruits, however, do not serve regularly as hosts of the melon fly. 
Only in rare instances does the melon fly attack them, and then 
only slightly. For practical purposes aside from quarantines all the 
fruits and vegetables listed under this subheading are free from 
attack by the melon fly, 

INTERESTING FACTS CONCERNING THE ADULT FLY. 

The most interesting facts about the adult melon fly center about 
the length of life and the capacity ta lay eggs, No flies have been 




Fig. 21. — Damage to squash by larva; of melon fly. Of the 
two fruits illustrated, the one to the right is normal, 
and the one to the left, the stunted and deformed fruit 
caused by melon-fly attack. (Authors' illustration.) 



THE MELON FLY. 



23 



known to live longer than 4^ clays without food and water, or longer 
than 5 days with water but no food. But if they can feed upon 
plant juices, such as the sap that exudes from cut or broken surfaces 
of pumpkin vines, cucumber fruits, papayas, etc., or the sap exuding 
from the breaks made in host plants during egg laying, adults may 
live many months. One female lived from February 17, 1914, to 
April 4, 1915, or 13| months. The length of adult life is variable 




Fig. 22. — Destruction of green bean pods by larvae of melon fly. In a and 6 a por- 
tion of the pods has been removed to expose larv.T and their work. In a are 
shown four well-grown larvae. Pods in different stages of drying out after the 
larvfe have left them are shown in c and d. (Authors' illustration.) 

under like conditions. From the standpoint of longevity the chief 
interest centers about the fact that certain adults may live long 
periods and thus keep the pest alive during seasons when host fruits 
are not in season. 

Female flies may begin to lay eggs as soon as 14 days after they 
emerge from the pupa during the warmer months, when the mean 
temperatures range from 75° to 79° F. During the winter, at a mean 



24 BULLETIN 643, V. S. DEPARTMENT OF AGRICULTURE. 



n 



of about 71° F., many adults may not lay until 44 days after emer- 
gence. The season of the year and the nature of their food have an 
influence upon the rapidity with which eggs are formed. 

But once the female fly begins to lay eggs, she may continue to do 
so throughout life. The largest number of eggs laid by any female 
in confinement is 687, but 1,000 probably may be. laid by vigorous 
long-lived flies. While 37 is the largest number of eggs laid by a 
single individual daring any one day, the number varies, and may 
be as few as 1. On many days no eggs are laid. Unlike the female 
of the Mediterranean fruit fly, which lays a few eggs almost daily, 
the female melon fly lays more eggs per day, but at greater intervals. 
Thus one fly deposited 14, 19, 13, 29, 16, 19, 16, 12, 17, 7, 9, 16, 7, 12, 
37, 25, 24, 21, 28, 6, and 18 eggs, respectively, per day during the first 
three months (summer months) after depositing her first eggs; she 
laid no eggs in fruits until she w^as 51 days old, and, after she began 
laying, laid eggs on only 21 out of 90 days. During the seventh, 
eighth, and ninth months of her life (winter months) she deposited 
10^, 2, 18, 14, 15, 20, 13, 9, and 3 eggs. 

Female flies can resume normal egg laying after periods of scarcity 
of host fruits. Females that have not been given an opportunity to 
lay eggs within fruits for periods ranging from 3 to 9 months after 
emergence have begun to deposit eggs at a normal rate as soon as 
fruits were placed with them in the laboratory rearing cages. 

WHY THE MELON FLY IS A SERIOUS PEST. 

The melon fly is a serious pest in Hawaii because it finds in the 
coastal areas a favorable climate and plenty of food. Regardless of 
the great discouragement due to its ravages, the oriental market 
gardeners, and others to a less extent, plant its host vegetation in 
rotation on the same or neighboring plats of ground. No attempt is 
made to prevent the flies from maturing in infested fruits. The de- 
caying and infested fruits of the cucumber crop, for instance, are 
left on the field that is to be planted to tomatoes, or the flies develop- 
ing from the cucumbers migrate to attack the melons just coming 
into bearing in the near-by field. No system of control, aside from 
covering successfully a small portion of the fruit that sets, is prac- 
ticed. 

It thus happens that large numbers of adults mature, and, as the 
climate is favorable, they multiply rapidly. During the warmest 
Hawaiian weather, when the mean temperature averages about 79° 
F., the egg, larva, and pupa stages may be passed in as few as 12 or 
as many as 29 days, according to the individual and its host. The 
complete life cycle is subject to great variation, according to the 



THE MELOlSr FLY. 25 

longevity of the adult. Since one female fly has been known to live 
431 days, it is evident that the complete life cycle from the laying of 
the egg to the death of the fly may be 443 to 460 days when the im- 
mature stages are passed during the warmer portions of the year. 
At an average mean temperature of about 68° F., which is the coolest 
temperature found in Hawaii where fruits are available in numbers 
for stud}^, the immature stages are passed in 40 to 45 days. It is 
difficult to state just what the variation in the life cycle may be in 
colder climates, but it may range between 3 and 4 months. 

This rapidity of increase throughout the coastal regions permits 
from 8 to 11 generations of the melon fly a year, when a generation is 
considered to extend from the time the egg is laid until the female of 
the next generation begins to deposit eggs. As the females are 
capable of living many months and of depositing eggs at frequent 
intervals throughout life, the generations become hopelessly mixed. 
It is possible for a female oA'ipositing on January 1 to be still alive 
and laying eggs the following January along with the progeny of 
11 generations of her descendants. It is, therefore, small wonder 
that the melon fly, under such favorable conditions, swarms through- 
out the market gardens of Hawaii and leaves little unaffected that is 
not protected by man. 

CONTROL MEASURES. 

NATURAL CONTROL. 

No agencies at present lire working in the Hawaiian Islands to 
bring about, even periodically, a very large natural reduction in the 
abundance of melon flies. The mortality among the immature stages, 
or among the adults, is not sufficiently high to be of practical value, 
although sometimes 90 per cent of the larvae may be found dead in 
certain decaying fruits. 

In climates colder than that of the Hawaiian coastal areas mor- 
tality due to cold temperatures will play a particularly active part 
in reducing the pest. While the cooler weather of the winter months 
does prolong the period of development throughout the coastal re- 
gions, the long life of the adult flies and the capacity of females for 
continued egg-laying make it difficult for market gardeners to benefit 
to any marked extent from the effects of cool weather if they allow 
their fruits to remain unprotected. The cooler weather in the more 
isolated gardens holds down the number of adults and limits their 
activity to a fewer hours during the day when it is warm enough for 
them to attack fruits, and in this way makes possible greater success 
in saving fruits by the use of various protective coverings than fol- 
lows the use of the same measures during the summer months. 



26 BULLETIN 643, U. S. DiEPARTMENT OP AGRICULTURE. 



PARASITES. 



Hawaii has no native pajrasi^es that attack the melon fly, but the 
Hawaiian Board of Agriculture and Forestiy has introduced a para- 
site from India. This parasite ^ was introduced at Honolulu during 
the early part of 1916, and has been reared and distributed in large 
numbers, but it is not known yet whether it will check the ravages of 
the melon fly in a p^ractical manner. It has become established, how- 
ever, and promises to be useful. 

ARTIFICIAL CONTROL. 

Individual growers of vegetables in Hawaii are likely to be dis- 
couraged in the application of remedial measures for the control of 
the melon fly. Host fruits are grown in rotation in the numerous 
garden spots and market-garden areas chiefly by uneducated orien- 
tals, who do not appreciate the necessity for a united fight against 
the fly. The usual custom among these laborers is to permit infested 
fruits to decay in the field. In certain uncultivated areas the wild 
Sycos and Chinese cucumbers run wild and furnish fruits in which 
the melon fly can breed throughout the year, even though no culti- 
vated crops are grown. This abundance of cultivated and wild host 
fruits, coupled with a climate favorable for rapid multiplication, 
produces many adult flies which spread in all directions to render 
valueless all remedial measures except those that involve protective 
coverings for the fruits. 

It thus happens that no artificial control measures have been 
applied successfully in controlling the melon fly under Hawaiian 
conditions. The only means now employed to safeguard fruits is 
that of protecting the 3'oung fruits with some type of covering until 
they are large enough to withstand attack. Trapping adults has 
proved a failure, and killing them by spraying thus far has given 
poor results. If all growers would cooperate systematically (1) in 
the destruction of the eggs and larva? by submerging infested fruits 
in water or by boiling and (2) in the destruction of the adults by 
spraying, the value of spraying with a poisoned bait and of covering 
the young fruits would be enhanced to a point where either might 
be sufficiently effective to be recommended as satisfactory. But so 
long as the cultivation of host plants is largely in the hands of 
orientals and others who do not appear to be amenable to instruc- 
tion as modified by western standards, no relief can be expected. 



Since adult melon flies do not deposit eggs for 2 to 4 weeks after 
emergence during the summer, and only after relativel}^ longer periods 

* Opius fletcheri Silv. 



THE MELON PLY. 27 

during the wintea', but feed continuously throughout this period, it 
is evident that any spray that will kill them before they begin to lay 
eggs is valuable. A poisoned-bait spray^ containing 5 ounces of lead 
arsenate in paste form, 2^ pounds of brown sugar, and 5 gallons 
of water, is very effective in killing adults. This spray, used at the 
rate of 30 gallons to the acre, was applied by means of a knapsack 
sprayer. About 2 acres of Chinese melons and cucumbers in a field 
fairly well isolated, from the Hawaiian standpoint, which means 
that no host fruits were growing within 500 yards, were sprayed on 
May 21, 26, and 28^ June 1, 4, 8, 14, and 23 during typical summer 
weather. Six hours after an application many adults were sluggish 
and flew with difficulty, but within 24 hours many dead adults could 
be found among the vines. Although the adults were lessened nu- 
merically by the spray, the young fruits were punctured as badly at 
the end of the experiment as at the beginning. 

Although negative results have followed the use of poisoned-bait 
sprays in Hawaii, failure has been due to the peculiar conditions sur- 
rounding the fields sprayed that permit an influx of female flies. 
Under commercial conditions, where cantaloupes, pumpkins, and 
watermelons are grown in large quantities in fairly dry climates, it is 
reasonable to believe that sufficiently good results will follow the 
use of poisoned sprays to make their application practicable as a 
method of control. 

DESTRUCTION OF INFESTED FRUITS. 

Larvae and eggs may be killed by submerging the infested por- 
tions of the plant in water, or b}^ burjdng, boiling, or burning. Choice 
of method will depend largely upon the amount of fruit to be 
handled and upon local conditions. There is no surer way to kill all 
immature stages than to boil or burn the fruits. Burning is often 
expensive, and, when trash in compost holes is depended upon to 
furnish the fuel, is likely to be unsatisfactory, particularly where, as 
in Honolulu, the quantity of infested material is so great. Bringing 
infested fruits to the boiling point will kill all forms. The sub- 
merging of fruits in ordinary tap water for five days will either 
kill all larvae and eggs or stop further development. 

Burial in soil is a satisfactory method, provided the fruits are 
buried deep enough and cracks are prevented from developing in 
the earth above the fruits as the latter decay and settle. It must 
be remembered that just after transforming from the pupa the 
adults are so soft that they can force their way through very small 
openings. A crack in the soil extending down to the fruit, even 
though it be no wider than ordinary blotting paper, is still wide 
enough to allow the adults to reach the surface and thwart the pur- 
pose of fruit burial. Adults can not make their way through a foot 



28 BULLETIN 643, U. S, DEPARTMENT OF AGRICULTURE. 

of weil-tamped soil, but have been known to force their way throiigli 
2 to 3 feet of dry loose sand beneath which their pupae had been 
buried. 

Because burial and burning may be left to subordinates who may 
not have the interests of the owner so much at heart, boiling or sub- 
mergence in water is more highly recommended. The larvae will 
not injure cattle if the fruits are used as feed, but many larvae may 
escape before they are eaten ; hence this method of destruction is not 
recommended unless the fruits have a real value as a food. 

PliOTECTIVE COVERINGS. 

The protection of fruits and plants by covering with soil, pa,per, 
or cloth is a great labor-consuming operation, yet this is the only 
method that will protect under present Hawaiian conditions. Even 



Fig. 23. — Protecting cucurbits from attack by melon flies. Each fruit (in tliis case 
of Momordica sp. ) is placed, immediately after it has been fertilized, within a long 
envelope made of newspaper. (Authors' illustration.) 

as practiced to-day, less than 25 per cent of all fruits covered, except 
certain Chinese marrows, are actually saved from attack. In a 
slightly cooler climate than that of coastal Hawaii a high percentage 
of the fruits could be saved. As it is, the great attraction of the un- 
fertilized ovaries of the bloom makes it difficult to put on coverings 
before the flowers are infested. During the warmer portions of the 
year the bloom of cucurbits, with the exception of the cucumber, should 
be protected at least three to four days before the flower unfolds. 
At present many fruits are covered, but rather indifferently and 
ineffectively. During April only 9 out of 43 fruits of the Chinese 
melon that had been covered were sound, while on the same datfe 119 



THE MELON FLY. 29 

out of 692 young protected watermelons were actually free from in- 
festation. 

Certain Japanese growers ward off attack by burying the young 
fruits in the soil or by surrounding them with straw or trash until 
they are sufficiently old to withstand fatal attack. In certain light 
soils cantaloupes are kept buried in the soil until they are ripe and 
they appear upon the market almost white in color. The most suc- 
cessful of protective coverings are those shown in figure 24. In this 
case the Momordica vines are grown over bushes, hence the young 
fruits can be found easily and inclosed in long cases made from 
newspapers and resembling envelopes cut across at both ends. These 
cases are left open at the lower end, but are never entered by the 
adult flies. 

MEASURES TAKEN TO KEEP THE FRUIT FLIES OF HAWAII FROM 
GAINING A FOOTHOLD IN CONTINENTAL UNITED STATES. 

The Federal Horticultural Board, by means of its Quarantine 
No. 13, entitled "Mediterranean Fruit Fly and Melon Fly," issued 
March 23, 1914, is doing all that man can do to prevent the two 
fruit-fly pests of Hawaii from becoming introduced into main- 
land United States. The regulations of the quarantine practically 
have put a stop to the movement of fruits and vegetables from 
Hawaii. Certain fruits and vegetables, however, such as bananas 
of the noncooking type, pineapples, taro, and coconuts, and others, 
when it can be shown to the satisfaction of the Department of Agri- 
culture that in the form in which they are to be shipped they are 
not and can not be a means of conveying either the Mediterranean 
fruit fly or the melon fly, may be moved or allowed to move from 
Hawaii into or through any other State, Territory, or District of 
the United States when they have been inspected by the United 
States Department of Agriculture, certified to be free from infesta- 
tation, and marked in compliance with the regulations. Pineapples, 
taro, and coconuts do not support the fruit flies of Hawaii, neither 
do bananas when shipped according to trade requirements. In prac- 
tice the quarantine eliminates all shipments of fruit except the four 
just mentioned, and of these pineapples and bananas only are regu- 
larly shipped. 

The enforcement of the quarantine is divided between the repre- 
sentative of the board in Hawaii and those at the ports of entry to 
the mainland, notably San Francisco, San Pedro, and Seattle. In 
Hawaii it is the duty of the inspector to see that the fruit is grown 
under conditions reasonably sanitary from a fruit-fly standpoint, that 
each package or bundle offered for shipment is inspected and bears a 
certificate to that effect, and that transporting companies do not re- 



30 BULLETIN 643, U. S. DEPARTMENT OF AGEICULTUKE. 

ceive for shipment consignments of fruit unless they have received 
from the Federal Horticultural Board a permit for such action. 
These permits, which give data on the kind, amount, and origin of 
fruit, the name and address of consignor and consignee, and dates, 
are issued in triplicate; the duplicate and triplicate remain* in the 
files of the transporting compan_y and the Federal Horticultural 
Board, respectively. The original is attached to the bill of lading 
accompanying the shipment and no consignment of fruit is permitted 
to leave the ship at the port of destination unless this permit is pre- 
sented to the Federal inspector. 

The duty of the inspector at the mainland ports is to make certain 
that no express or freight consignments leave ships arriving from 
Hawaii unaccompanied by the permit above mentioned, and that no 
quarantined fruits or vegetables are present either in the ship's lock- 
ers as ships' stores or in the possession of passengers, for all such are 
contraband after the ship passes within the 3-mile limit of the main- 
land. The inspector of the port of entry also must receive from each 
passenger a statement that he has in his baggage no contraband fruits 
or vegetables. Inspectors also have the right to search the personal 
belongings of passengers and members of the crew. 

There seems little danger of fruit-fly pests reaching ihe mainland 
from Hawaii in commercial consignments of fruit since Quarantine 
No. 13 went into effect. The greatest clanger at present lies in the 
careless introduction of the pests hy miinformed travelers who^ with- 
out appreciating the great fiiw/ifwial losses the' Goverivment is attempt- 
ing to avert^ persist in concealing ahout their persons and haggage 
contraband fruits^ or in: sending these hy express or post in packages 
the contents of which are not stated tT^thfuUy. These are the a.ve- 
nues of introduction that no law can close thoroughly. To close them, 
honesty and cooperation with the Federal Horticultural Board on the 
part of all are necessary. 

SUMMARY. 

The melon fly, a native of the Indo-Malayan region, is one of a 
number of very destructive pests that are likely to be introduced into 
the mainland United States. The quarantine officers of the Federal 
Horticultural Board and of California are each year intercepting it 
in infested fruits at California ports on ships from the Hawaiian 
Islands. 

The melon fly was introduced into Hawaii about 1895 by Japanese 
immigrants in fruits which they brought with them as food from 
Japan. Before its arrival in Hawaii, cantaloupes, watermelons, toma- 
toes, and all kinds of cucurbitaceous crops, such as pumpkins, 
squashes, cucumbers, etc., were grown in large quantities and were 



THE MELON FLY. 31 

cheap. They could be grown in every dooryard. Because of the 
ravages of the pest, these crops can not be grown now by the average 
person, and only with great difficulty in market gardens. Many 
fruits must be imported, and the cost of all has been increased as a 
result of melon-fly attack. Even cowpeas and string beans may be 
infested. It is impossible to overstate the destructiveness of the 
melon fly to cucurbitaceous crops under Hawaiian coastal conditions, 
where none of these can be brought to maturity except with the 
exercise of the greatest care on the part of market gardeners. 

Since there are as many as 8 to 11 generations of the melon fly a 
year, and the female flies may live to be over a year old and lay eggs 
throughout life, the pest can multiply very rapidly. No agencies 
have been found to.be working at present in- Hawaii that bring about, 
even periodically, a great natural reduction in the abundance of 
melon flies. No native parasites are known to attack the melon fly, 
but it is hoped that the parasite introduced from India during 191G 
may prove effective. In colder climates cold weather will prove a 
marked and valuable control factor. Predacious enemies and several 
forms of mortality recorded are of no practical value under Hawaiian 
conditions. 

No satisfactory artificial measures have been applied' successfully 
in combating the melon fly under Hawaiian conditions. Poisoned- 
bait sprays promise to yield effective results under other cultural con- 
ditions. In Hawaii these sprays would be effective if they w^ere used 
consistently and universally, but they are not. At presen^t cucurbits 
can be grown only by the use of coverings of various sorts for the 
protection of the very young fruit. Killing the immature stages by 
submergence in water, by burial in soil, or by boiling are not applied 
as methods of control, although they are effective when intelligently 
applied. Artificial methods of control are not likely to prove satis- 
factory in Hawaii so long as the growing of the chief host plants 
remains in the hands of uneducated oriental laborers who do not 
practice clean cultural methods or cooperate in applying remedial 
measures. 



PUBLICATIONS OF THE U. S. DEPARTMENT OF AGRICULTURE 
RELATING TO INSECTS INJURIOUS TO CITRUS AND OTHER 
SUBTROPICAL FRUITS. 

AVAILABLE FOR FREE DISTRIBUTION BY THE DEPARTMENT. 

Control of the Citrus Thrips in California and Arizona. (Farmers' Bulletin 

674.) 
Carbon Disiilphid as an Insecticide. (Fai*niers' Bulletin 799.) 
Common Meal.vbug and its Control in California. (Farmers' Bulletin 862.) 
Fumigation of Ornamental Greenhouse Plants with Hydrocyanic-acid Gas. 

(Farmers' Bulletin SSO.) 
Fumigation of Citrus Trees. (Farmers' Bulletin 923.) 

Control of the Argentine Ant in Orange Groves. (Farmers' Bulletin 928.) 
Spraying for the Contx'ol of Insects and Mites Attacking Citrus Trees in 

Florida. (Farmers' Bulletin 933.) 
Citrus Fruit Insects in Mediterranean Countries. (Department Bulletin 134.) 
The Mediterranean Fruit Fly iu Bermuda. (Department Bulletin 161.) 
Argentine Ant: Distribution and Control in the United States. (Department 

Bulletin 377. ) 
The Citrus Thrips. (Department Bulletin 616.) 
The Mediterranean Fruit Fly. (Department Buleltin 640.) 
Some Reasons for Spraying to Control Insect and Mite Enemies of Citrus Trees 

in Florida. (Department Bulletin 645.) 
The Argentine Ant in Relation to Citrus Orchards. (Department Bulletin 

647.) 
Preparations for Winter Fumigation for Citrus White Fly, (Entomology 

Circular 111.) 
Spraying for White Flies in Florida. (Entomology Circular 168.) 

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, GOVERNMENT PRINTING 
OFFICE, WASHINGTON, D. C. 

Kat.vdids In.iurious to Oranges in California. (Department Bulletin 256.) 

Price. 10 cents. 
The Melon Fly in Hawaii. (Department Bulletin 491.) Price, 25 cents. 
Fumigation of Ornamental Greenhouse Plants with Hydrocyanic-acid Gas. 

(Department Bulletin 513.) Price, 5 cents. 
Mango Weevil. (Entomology Circular 141.) 1911. Price, 5 cents. 
Fumigation for Citrus White Fly, as Adapted to Florida Conditions. (Ento- 

molog.v Bulletin 70.) 190S. Price, 15 cents. 
Fumigation Investigations in California. (Entomology Bulletin 79.) 1909. 

Price, 15 cents. 
Hydrocyanic-acid Gas Fumigation in California. (Entomology Bulletin 90, 

3 pts.) 1013. Price, 20 cents. 
Fumigation of Citrus Trees. (Entomology Bulletin 90, pt. I.) 1913. Price, 

20 cents. 
Value of Sodium Cyanid for Fumigation Purposes. (Entomology Bulletin 90, 

pt. II.) 1913. Price. 5 cents. 
Chemistry of Fumigation with Hydrocyanic-acid Gas. (Entomology Bulletin 

90. pt. III.) 1913. Price, 5 cents. 
White Flies In.iurious to Citrus in Florida. (Entomology Bulletin 92.) 1911. 

Price, 25 cents. 
Orange Thrips, Report of Progress. (Entomology Bulletin 99, pt. I.) 1911. 

Price, 5 cents. 
Red-banded Thrips. (Entomology Bulletin 99, pt. II.) 1912. Price. 5 cents. 
Natural Control of White Flies in Florida. (Entomology Bulletin 102.) 1912. 

Price, 20 cents. 



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